Developments in the business world have led to an increasing demand for greater precision in the calculation of interest. For example, parties whose business dealings involve using bank services can agree with the banks that particular conditions will call for particular corresponding interest rates to apply to sums deposited in or borrowed from the banks. The conditions might depend on such factors as the calendar day: that is, on whether it is a workday or weekend day, a public holiday, the last workday of the month, a public holiday in a country that has a strong influence on financial markets (e.g., July 4), and the like. Users of bank services also may agree to let events in financial markets affect the way interest is calculated on a given calendar day. An example of such an event is an “option expiration,” which may occur at regular intervals in a stock exchange. For example, on the third Friday of the third month of each quarter, index futures and options on the Eurex options and futures exchange on the German Stock Exchange (DAX) expire. Typically, on an option expiration day, large market participants, such as fund managers, try to force options and futures prices to the level equivalent to their investment on the options and futures market.
Known business software typically may only allow a user to discriminate with respect to working days and non-working days (i.e., typically, week days vs. weekends and public holidays), for whatever purposes this distinction might be relevant. However, discrimination with respect to calendar days with only this coarse degree of variability is not able to adequately reflect the increasing variability in the way the calendar may affect an interest calculation. Accordingly, in view of the greater demand for more precision in interest calculation, an approach is called for to reflect such variability.